Yahoo and Tumblr made their wedding vows Monday with the stumbling Web search giant publicly announcing its promise not to “screw up” the relationship.

Yahoo confirmed it will buy the blogging website for $1.1 billion cash, in a bold move to make itself more relevant amid the explosion in social media on the Internet.

It was old new media hooking up with new new media. Even as Yahoo’s CEO Marissa Mayer took to social media to announce the deal, promising “not to screw it up,” David Karp, the 26-year-old wunderkind who heads Tumblr celebrated the acquisition with a blog post that signed off with “F*** yeah, David.”

Perhaps trying to assuage Tumbler users who are concerned that Yahoo would irrevocably alter the blogging site’s edgy image, Yahoo said Tumblr will operate independently as a separate business.

“David Karp will remain CEO. The product, service and brand will continue to be defined and developed separately with the same Tumblr irreverence, wit, and commitment to empower creators,” the statement said.

Marissa Mayer’s own Tumblr post showed some of that irreverence with a GIF that seemed to poke fun at all the worries about the deal. “Now panic and freak out,” “Keep calm and carry on,” “Yahoo,” “Tumblr” the GIF said in successive, pastel-colored panels. Mayer also posted a tweet that had the Internet buzzing a bit with some mild ribbing.

“Before touching on how awesome this is, let me try to allay any concerns: We’re not turning purple. Our headquarters isn’t moving. Our team isn’t changing. Our roadmap isn’t changing. And our mission – to empower creators to make their best work and get it in front of the audience they deserve – certainly isn’t changing,” Karp, who dropped out of high school at 15 to start the company, said in his blog post.

News of the deal was widely leaked Sunday. Talk of a deal began circulating Friday, after the Wall Street Journal’s All Things D reported that the two companies had been in talks for several weeks.

Since Marissa Mayer became CEO at Yahoo, the company has acquired several companies that appeal to younger audiences, including Summly, Astrid and Jybe. Yahoo has also been rumored to be eyeing Hulu.

Observers say Mayer is making these deals to attract a younger audience.